Thermoset molding compositions known in the art are generally thermosetting resins containing inorganic fillers and/or fibers. Upon heating, thermoset monomers initially exhibit viscosities low enough to allow for melt processing and molding of an article from the filled monomer composition. Upon further heating, the thermosetting monomers react and cure to form hard resins with high stiffness.
One potential industrial use of thermoset compositions is electrical applications and under hood components such as engine valve covers. Electrical applications typically require specific dielectric properties that are dependent upon the application. Under hood components preferably exhibit high strength, high ductility and high modulus at elevated temperatures. It is also preferred that the dimensions of the molded parts conform closely to those of the molds used to prepare them.
U.S. Pat. No. 6,352,782 to Yeager et al. describes thermoset compositions comprising poly(arylene ether) resins that have been capped with ethylenically unsaturated groups. These compositions exhibit desirable properties including high glass transition temperatures and low coefficients of thermal expansion. However, these materials are not suitable for all applications.
There remains a need for thermoset compositions that can provide excellent mechanical properties and application specific properties such as dielectric strength and high modulus.